A variety of Factors involved in the blood clotting process have been identified, including Factor VII (FVII), a plasma glycoprotein. Haemostasis is initiated by the formation of a complex between Tissue Factor (TF) being exposed to the circulating blood following an injury to the vessel wall, and Factor VIIa which is present in the circulation in an amount corresponding to about 1% of the total Factor VII protein mass. Factor VII exists in plasma mainly as a single-chain zymogen which is cleaved by FXa into its two-chain, activated form, Factor VIIa. Recombinant activated Factor VIIa (rFVIIa) has been developed as a pro-haemostatic agent. The administration of rFVIIa offers a rapid and highly effective pro-haemostatic response in haemophilic subjects with bleedings, who cannot be treated with other coagulation Factor products due to antibody formation. Also bleeding in subjects with Factor VII deficiency or subjects having a normal coagulation system but experiencing excessive bleeding can be treated successfully with Factor VIIa.
The purification and handling of Factor VII must be careful, due the possibility for degradation of the molecule. Factor VII and Factor VIIa, being large molecules (approx. molecular weight 50 kD), are susceptible to mechanical degradation by shear forces during purification and filtration. Further, Factor VIIa is an active proteolytic enzyme that degrades other proteins including Factor VIIa. Degradation of Factor VIIa mainly involves cleavage in the heavy chain of Factor VIIa, particularly at amino acids no. 290 and 315 in the molecule. Finally, methionine residues in Factor VII and Factor VIIa may be oxidized.
An object of the present invention is to provide a method for the removal or inactivation of viruses from liquid Factor VII compositions by which method the integrity of the Factor VII constituents is substantially preserved.
WO 96/00237 discloses a method of virus-filtration of a solution that contains a macromolecular, e.g. a protein such as the plasma protein Factor IX.
WO 98/37086 discloses removal of viruses from plasma-derived protein solutions by nanofiltration using a membrane having an average pore size of 15 nm.
Tomokiyo et al., Vox Sanguinis, 2003, 84, 54-64, disclose the large-scale production of human plasma-derived activated Factor VII concentrate. The method of production involves the step of virus-filtration of a solution comprising inactive Factor VII.